Materials Science Forum Vol. 589

Abstract: Continuous hot dip galvanized steel samples have been treated with traditional chromium(VI)-containing passivator and environment friendly rare-earth metal containing ceriumsalt and lanthanum-salt based solutions using different immersion times. The treated surfaces have been examined by scanning electron microscope equipped with an energy dispersive X-ray analyser. After the pre-treatment the samples have been spray-painted with epoxy-based organic paint. The adhesion was tested with bending and cross-cut test. Thereafter salt spray test was performed on duplex systems. After 48 hours samples have been taken out from the corrosion chamber in order to perform electrochemical impedance measurements for 24 hours. Based on the results the most promising passivation among the chromium(VI)-free solutions has been found to be the cerium-salt based treatment. The adhesion of the organic coating was better on cerium-chloride treated substrate than on chromated one, while the anti corrosion properties of the two duplex systems were comparable.

Abstract: Characteristics of 3D printed specimens are porous structure and low mechanical strength. Due to porous structure post treatment is possible, and in most cases infiltration with an epoxy resin, wax or cyanoacrylate material takes place. As a result of post treatment, the mechanical strength can be increased by 100%, although this is strongly influenced by the infiltration depth that depends on the porous structure and the resin viscosity. In the framework of the common research of the Department of Polymer Engineering, BME and Varinex Zrt. the applicability of a 3D printer is examined in the field of direct tool making. As the first step, the resin uptake ability of specimens prepared with a Z810 3D printer is examined.

Abstract: This paper gives an overview of the laser cutting equipment developed for stent cutting: Nd:YAG, fiber and water-jet guided lasers; work piece positioning systems and different materials for stent manufacturing were presented. The side effects of laser cutting like oxide layer, heat affected zone and dross deposition were examined. Pulsed Nd:YAG laser cutting of AISI 304L type austenitic stainless steel high precision tube with 1,800 mm diameter and 0,117 mm wall thickness was performed. The relationship between the average power and kerf was characterised.

Abstract: Protective, chromate substitute thin layers on roughened galvanized surfaces produced at OCAS (Arcelor, Belgium) were characterized and compared using Scanning Electron Microscopy (SEM+EDS), Atomic Force Microscopy (AFM), Nanoindentation and X-ray Photoemission Spectroscopy (XPS). EDX maps, line scans and point analyses obtained at various places of the surfaces have shown differences between the CVD and silane nanolayers in the matter of thickness distribution and composition. At cross-section specimens the thickness of the layers could be shown. The hardness differences caused by layer thickness variations are hard to follow by nanoindentation as the penetration depth of the indenter is much larger than the thickness of the coatings. XPS measurements can distinguish between the chemical states of silicon in CVD and silane coatings.

Abstract: There is no doubt that concrete makes a massive contribution to sustaining the quality of life. Properties of concrete can be expediently modified by adding special chemical materials called admixtures. Admixtures for concrete are now widely accepted as materials that contribute to the production of durable and cost-effective concrete structures [1]. Plasticizing admixtures reduce water needed to achieve a given workability of the fresh mix. This main effect can be utilized in three ways: increased strength, increased workability, or economies in mix design [2]. In this research work effect of type and dosage of different plasticizing admixtures available in Hungary were investigated in detail. Standard test methods such as flow table test, compressive test, and shrinkage test were applied to obtain effectiveness of the admixtures. Results were compared with the requirements of the harmonized admixture standard MSZ EN 934-2:2002.

Abstract: Concrete is the strongest candidate to be the most important construction material of the 21st century. This can be ensured by the continuous research and development of new materials and technologies regarding concrete construction. Properties of concrete can be expediently modified by adding special chemical materials called admixtures. In this research work effect of type and dosage of different superplasticizing admixtures available in Hungary were investigated in detail. Standard test methods such as flow table test and compressive test were applied to obtain effectiveness of the admixtures. Regarding the examinations done in the course of the research, we refer to the regulations of the EU harmonized admixture standard currently valid in Hungary MSZ EN 934-2:2002. In connection to that we will precisely quote the requirements specified in the standard regarding superplasticizers and will also mention the main differences compared to the plasticizer additives. Types, properties and use of superplasticizers are introduced in detail, too. Experimental results are evaluated to rate the efficiency in compliance with the requirements of the standard.